1. Field of the Invention
The present invention relates to electric storage battery powered vehicles and more particularly relates to over-the-road vehicles which utilize prime movers formed by on-board traction batteries and electric motors.
2. Prior Art
Storage battery powered electric motor driven vehicles have been known and used in various forms for many years. One early usage was as passenger cars but because of the size, cost and weight of the necessary traction batteries, along with their limited driving ranges, early passenger vehicles were not desirable compared to internal combustion engine driven vehicles. Commercial production of over-the-road electric passenger vehicles has been virtually nonexistent for many years.
Electric battery powered vehicles have remained in use for relatively specialized purposes, most notably as lift trucks, power dollies, etc., in and around industrial plants. These vehicles have been particularly advantageous because they do not produce noxious exhaust emissions, operate quietly, and are not required to be operated long distances over terrain at high speeds. In industrial applications the vehicles have usually been provided with regular scheduled maintenance and servicing as needed which has reduced the necessity for providing certain safety features which might be required in vehicles which do not receive regular maintenance.
These vehicles have not operated like internal combustion engine powered vehicles with which most of the populace has been familiar, and merely operating them in a safe manner has required a certain degree of experience on the part of the operator. When the traction batteries are connected to the vehicle motor, for example by actuating a key operated switch, the vehicle is fully prepared to operate as soon as an accelerator pedal is depressed or some other similar speed controlling member is actuated. Inexperienced operators, accustomed only to driving engine driven vehicles, tend to be unaware of the operating status of the battery operated vehicle because the vehicle normally remains totally silent and vibration free when the key switch is closed and there is no starting sequence, as is required in an engine driven vehicle. Inexperienced operators have thus tended to cause collisions between the electric vehicles and adjacent objects when the vehicles are inadvertently accelerated. Accordingly, in industrial applications relatively experienced personnel have operated the vehicles to insure against safety hazards.
Specialized traction battery chargers have also generally been required for recharging traction batteries of the vehicles. The prior art chargers have normally included transformers and associated electrical circuitry to accommodate available power supplies to charging voltage levels required by the traction batteries. The chargers have been relatively large, heavy and were normally stationed appropriately so that the vehicles could be driven to the chargers for periodic recharging. In some applications, the chargers were constructed for operation from polyphase power supplies which were available at a limited number of locations in a typical industrial facility. Furthermore, these chargers were relatively inefficient in that only about 80% of the power supplied to the chargers was actually utilized to charge the batteries.
Because of their weight, which is frequently due to the inclusion of a power transformer, the prior art chargers have not usually been installed on vehicles so that payloads can be maximized and power requirements for operating the vehicle reduced. The traction battery chargers have also been relatively expensive to purchase thus making the use of a few chargers for a larger number of vehicles practical. Vehicle traction batteries have thus not generally been rechargeable by supplying charging power directly to the vehicle, nor have the vehicles normally been rechargeable from a conventional A.C. "household" power supply outlet (e.g., 110-volt or 220-volt outlets).
In some facilities additional traction battery units have been obtained so that charged battery units are used as replacements for battery units which require recharging. This practice has enabled the chargers to be used to recharge batteries while the vehicles remain in service. Obtaining additional traction batteries is expensive and requires use of battery handling equipment to replace and recharge traction batteries which have been removed from the vehicle.
Recently advantages of electric powered vehicles, i.e., the absence of polluting emissions and minimal noise levels created during their operation, in addition to the lack of requirement for directly burning any fossil fuels for propulsion, have resulted in renewed interest in possible widespread usage of storage battery powered over-the-road vehicles. Advances in the construction of traction batteries, vehicles, and electric motors over the years have tended to enable weight reductions of electric over-the-road vehicles while increasing their efficiency. Furthermore reductions in fossil fuel availability at low cost has reduced the operating cost savings of internal combustion engines over electric prime movers.
Generally speaking, the practices developed in connection with recharging batteries of industrial-type electric vehicles have not been such that they can be easily adopted for use with over-the-road private passenger vehicles both because of the expense involved and the inconvenience to private nonindustrial users. Likewise the vehicles themselves are not readily adaptable to over-the-road passenger vehicle usage because of their weight, limited range, and low operating speeds.
While some general use over-the-road electric powered vehicles have been proposed, the prior art has not always provided vehicles which are: easily operated by relatively inexperienced and/or unskilled drivers who may be accustomed to operating only engine driven vehicles; rechargeable by users who may not have any appreciable degree of knowledge or sophistication in the use and operation of electrical equipment; rechargeable without requiring specialized expensive equipment and/or specialized electrical power supplies (such as polyphase power supplies which are usually only available at substantial cost for industrial usage); and, of relatively fail-safe construction so that the vehicles can be operated safely in the absence of regular maintenance and servicing.